The present invention relates to a cooling structure for computers with heat generating components such as CPUs, and more particularly to a cooling device suitable for use in a cooling system that employs a heat transport and radiation means using a coolant, such as a heat pipe and a liquid-cooling system.
In recent years, devices and integrated circuits used in information processing apparatuses, such as personal computers and servers, tend to generate an increasing amount of heat because of their ever-increasing integration degree. CPUs in particular show a significant increase in the amount of heat produced because of their faster operation frequencies and enhanced integration.
Conventional personal computers and servers commonly employ, to cool the CPU generating much heat, a method of attaching a heat sink to the CPU to transfer the generated heat of the CPU to the heat sink and cooling the heat sink. Further, to dissipate heat to the outside of the computer, a cooling fan may be provided in the equipment for forced cooling.
To deal with an ever-increasing amount of heat generated by the CPU, the cooling capacity is enhanced by enlarging the heat sink and increasing the airflow of the cooling fan. The enlarged heat sink, however, leads to an increase in the size of the computer and the increased airflow of the cooling fan also results in a size increase of the computer due to the enlarged cooling fan. The airflow may be increased by increasing the revolution speed of the fan, but this method tends to increase fan noise.
Methods of radiating heat generated by CPU or the like that replace the heat sink include a heat pipe and a liquid-cooling system that transport heat by a coolant. These methods feature an increased degree of freedom in the structure because the coolant is cooled at a location remote from a heat-generating source such as CPU. In a case where a cooling fan is used to radiate the coolant-carried heat outside the equipment, however, problems similar to those described above arise.
Various methods have been proposed as solution for these problems. For example, JP-A-2000-154949 discloses a technique for thinning a cooling unit by arranging heat radiation fins with thermoelectric elements interposed therebetween around the outer circumference of a centrifugal fan. JP-A2000-77877 discloses a technique for reducing the thickness of a cooling unit by using a centrifugal fan thinner than heat generating parts. Further, JP-A-10-213370 discloses a technique for securing a necessary cooling air flow by transporting heat generated by the heat source such as CPU to a location near the power supply by means of a liquid-cooling system and then cooling a heat-carrying medium by a larger power supply fan.
When the conventional techniques described above are used to deal with the recent trend for an ever-increasing amount of heat generated by the CPU, the following problems are observed. In JP-A-2000-154949, for example, the cooling air is not directly applied to the heat-generating component but is applied to the fins. Hence, if the fin height is limited for the thinning, there is a limit on the cooling performance. Further, in JP-A-2000-77877, a fan thinner than the heat generating component is required and this makes it difficult to secure a necessary air flow of the fan, imposing a limit on the cooling performance. JP-A-10-213370, on the other hand, requires increased thicknesses of the fan and heat exchanger, making it difficult to reduce the thickness of a cubicle or case.
In a computer with a cooling structure using a heat transport measure such as a heat pipe and a liquid-cooling system, it is an object of the invention to provide a cooling system for the computer, which realizes a reduced thickness and an improved efficiency of a heat radiation unit.
To the above objective, a cooling device for radiation through a coolant to the outside heat generated by such heat generating portions as CPU in a computer comprises a heat receiving unit for transmitting the heat generated by a heat generating portion such as CPU to the coolant, and a heat radiation unit for dissipating the heat stored in the coolant to the outside by a radiator in which the coolant is filled. The heat-receiving unit and the heat radiation unit are connected together through a tube so that the coolant can circulate between them. The heat transferred to the coolant in the heat-receiving unit is dissipated to the outside by the heat radiation unit. Further, the heat radiation unit is arranged parallel to a printed circuit board on which the heat generating portion such as CPU is mounted, in order to increase a heat dissipating area of the radiator and therefore the amount of heat radiated. In this construction the coolant circulating through the tube absorbs heat, which was generated by the heat generating portion such as CPU and collected by a heat receiving head, and dissipates it outside through the radiator of the heat radiation unit.
The radiator has a cooling pipe, which contains the coolant, formed in a spiral or radial shape so that the coolant can flow from the central portion of the radiator toward its outer peripheral portion. With this construction, the heat from the heat-generating portion can be diffused from the central portion of the radiator toward the peripheral portion and dissipated from the radiator surface.
Further, the central portion of the radiator is provided with a cooling fan or a cooling air blowing opening for the forced cooling of the radiator. The cooling air is delivered perpendicularly to the radiator and the direction of airflow is changed on the radiator surface toward the circumferential direction. Alternatively, a centrifugal fan is used to generate a cooling airflow in the circumferential direction along the radiator surface. As a result, although the air flow speed decreases as the air flow nears the peripheral portion of the radiator, the forced cooling can be performed with high efficiency because the coolant also flows from the central portion toward the peripheral portion.
Further, a path of the cooling air is formed in one of the following two ways. One is to arrange the radiator on a side of the cooling unit where the CPU and so forth are mounted and thereby form the path between the radiator and the external case of the cooling unit. Another is to arrange the radiator in contact with the external case to form a gap for the cooling airflow path in the cooling unit.
In the latter case, not only can the radiator be forcibly cooled by the cooling air but the heat can also be dissipated by a natural convection through the external surface of the case. When the cooling air is delivered from the heat-generating portion on the CPU side, the cooling fan in the computer can also be used as the radiator cooling fan.